A conventional vertical processing furnace for processing semiconductor wafers may include a heating means, placed around a bell jar-shaped process tube and a cylindrical inner tube or liner that is coaxially disposed within the process tube. The upper end of the process tube may be closed, typically by a dome-shaped structure, whereas the lower end surface of the process tube is supported by a support flange. The liner may be open at both its upper and its lower end, with the lower end supported by the support flange as well. An inner space bounded by the liner and the support flange forms a process chamber in which wafers to be treated may be processed. Between the liner and the process tube is a circumferential space. The support flange is provided with an inlet opening for inserting a wafer boat carrying wafers. The wafer boat may be placed on a door that is vertically moveably arranged and that is configured to close off the inlet opening in the flange. Optionally, the wafer boat may be placed on a pedestal which in turn is placed on the top side of the door. The flange may further include at least one gas inlet opening that is in fluidum connection with the process chamber bounded by the liner. Additionally, the flange may include a gas exhaust that is in fluidum connection with the circumferential space. This gas exhaust may be connected to a vacuum pump for pumping off gas from the circumferential space.
A well-known problem of the conventional vertical processing furnace for processing semiconductor wafers consists of small particles contaminating the process chamber (and the semiconductor wafers placed within). This problem has been identified in various prior art, such as for example US 2012/0186573, US 2002/602c4505 and US 2007/0181066 in which various causes of contamination are discussed and associated solutions are disclosed.